Preparation of polystyrene microplastic particles by solvent-dissolution-precipitation

The reliable characterisation of the physicochemical properties of micro-sized plastic particles requires quality reference materials for establishing, calibrating, and validating methods. Heterogeneity in particle size, shape and surface chemistry are important factors for reference materials for them to mimic environmental microplastics. This paper introduces a method for preparing model polystyrene micro and nano plastic reference materials using a solvent dissolution-precipitation approach. Polystyrene microplastic particles with mean particle sizes of 0.35, 15.7, 30.0 and 52.3 micron were produced using solvent precipitation under different synthesis conditions with the particle present in a well dispersed and partially dispersed system. The particle size can be controlled by reducing the initial polystyrene-cyclohexane concentration and adjusting the volume of methanol. At a fixed polystyrene-cyclohexane ratio, particles within the specified size range were consistently produced. Chemical analysis using pyrolysis-gas chromatography-mass spectrometry revealed that synthesized microplastics maintain their chemical properties, aligning with the original composition of virgin polystyrene pellets. A similar conclusion was drawn after examining the surface chemistry of the virgin and synthesised microplastic particles using ATR-FTIR analysis. The polystyrene particles produced in this way may be of use as reference materials and might be of interest for toxicological studies.